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AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
228 PM EDT THU AUG 21 2014

.SYNOPSIS...
A BROAD UPPER LEVEL RIDGE OF HIGH PRESSURE WILL CONTINUE TO PROVIDE
VERY WARM TEMPERATURES ACROSS THE REGION INTO SATURDAY. A BACK DOOR 
COLD FRONT WILL THEN PUSH INTO THE AREA FROM NORTHEAST USHERING IN
COOLER TEMPERATURES STARTING SUNDAY.

&&

.NEAR TERM /THROUGH FRIDAY/...
AS OF 215 PM EDT...A PROMINENT 500 MB RIDGE AXIS WILL PERSIST OVER 
THE LENGTH OF THE MS RIVER VALLEY TONIGHT THROUGH FRI. CONVECTION 
ARISING FROM IMPULSES RIDING OVER THE UPPER RIDGE HAS ALREADY FILLED 
IN ON REGIONAL RADARS FROM SE KY TO WV THIS AFTN. HOWEVER...THE 
CONVECTION ALLOWING MODELS STILL SHOW THE BEST AFTN TSTM TRIGGERING 
OVER THE SRN MTNS WHERE LAPS SFC BASED CAPE VALUES ARE RUNNING 3000 
TO 4000 J/KG. THEN...THE MESOSCALE MODELS DEPICT THE WEAK CONVECTIVE 
SYSTEM TO THE N PASSING MAINLY NORTH OF THE AREA THIS EVENING. SOME 
TRAILING CONVECTION FROM THIS NRN SYSTEM MAY BRUSH THE NRN TIER FROM 
21Z TO 03Z. MAINLY MID AND HIGH DEBRIS CLOUDS SHOULD LINGER THROUGH 
THE NIGHTTIME HOURS...WITH ANY FOG AND LOW CLOUD ISSUES CONFINED TO 
THE SW MTN VALLEYS. EXPECT ANOTHER NIGHT OF MILD MINS...WITH MAINLY 
LOW TO MID 60S IN THE MTNS AND AROUND 70 ELSEWHERE.

THE FLOW PATTERN BETWEEN THE RIDGE AND A NEW ENGLAND LOW PRES SYSTEM 
WILL AMPLIFY ON FRI...WITH MORE NNW FLOW DEVELOPING ALONG THE 
APPALACHIANS BETWEEN THESE FEATURES. THIS SHOULD BRING THE NRN TIER 
OF THE FORECAST AREA A BIT MORE INTO THE PATH OF ANY UPSTREAM MCS 
ACTIVITY FROM THE OH VALLEY LATE FRI. IN ADDITION...SFC BASED 
INSTABILITY AND LAPSE RATES LOOK JUST A TOUCH MORE ROBUST FOR FRI 
AFTN...BUT STILL RELATIVELY UNIMPRESSIVE FOR SEVERE WX COMPARED TO 
UPSTREAM AREAS. OTHERWISE...WESTERLY DOWNSLOPING 850 MB FLOW THROUGH 
THE PERIOD WILL MAKE IT A STRUGGLE TO GET MUCH CONVECTION GOING FROM 
OTHER SOURCES...AND MAX TEMPS WILL LIKELY GAIN A DEGREE OR SO OVER 
THU VALUES. SRN PIEDMONT HEAT INDEX VALUES COULD SURPASS 100 FRI 
AFTN IF WE SEE SLIGHTLY LESS DEWPOINT MIXING.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/...
AS OF 210 PM THURSDAY...STRONG UPPER RIDGE WILL PERSIST OVER THE 
MISS VALLEY THROUGH THE PERIOD...PLACING MUCH OF THE SOUTHEAST AND 
MID-ATLANTIC WITHIN MODERATE N/NW UPPER FLOW. OUR AREA WILL 
THEREFORE REMAIN SUSCEPTIBLE TO /RING OF FIRE/ CONVECTION DEVELOPING 
NEAR QUASI-STATIONARY FRONTAL ZONE ACROSS THE OHIO VALLEY/CTRL 
APPALACHIANS REGION...WHICH COULD DROP INTO THE CAROLINAS IN 
SOMEWHAT ORGANIZED FASHION DURING THE AFTERNOON AND EVENING. 
THERMODYNAMIC PROFILES WILL REMAIN SUFFICIENT TO SUPPORT ISOLATED 
SEVERE WEATHER SATURDAY AFTERNOON/EVENING. 

BY THE END OF THE PERIOD...THE FRONTAL ZONE MAY BEGIN TO BACK DOOR 
ITS WAY INTO THE AREA BY EARLY SUNDAY...AS THE STILL-BUILDING UPPER 
RIDGE BEGINS TO SQUEEZE THE DOWNSTREAM UPPER LOW OFF THE EAST 
COAST...ALLOWING WEAK SURFACE RIDGING TO BUILD DOWN THE EASTERN 
SEABOARD. THEREFORE...IN ADDITION TO THE CONTINUED THREAT OF  
MIGRATION OF UPSTREAM CONVECTION INTO THE AREA...THE BACKDOOR FRONT 
MAY PROVIDE AN ADDITIONAL FOCUS FOR CONVECTION ON SUNDAY. HOWEVER... 
EXACTLY WHERE THE BEST CHANCES WILL OCCUR IS STILL SUBJECT OF 
DEBATE...AS THE AIR NORTH OF THE BOUNDARY MAY BE TOO STABLE TO 
SUPPORT MUCH IN THE WAY OF PRECIP CHANCES. THE HIGHEST POPS WILL BE 
FAVORED ACROSS THE SOUTHWEST ZONES...WHERE CONFIDENCE IN ADEQUATE 
INSTABILITY IS HIGHEST...AND A WEAK EASTERLY FLOW MAY PROVIDE AN 
ADDITIONAL SOURCE OF LIFT NEAR THE BLUE RIDGE. TEMPS WILL REMAIN 
ABOVE NORMAL UNTIL SUNDAY...WHEN MAXES WILL LIKELY BE BELOW NORMAL 
UNDER MORE EXTENSIVE CLOUD COVER AND E/NE FLOW.

&&

.LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/...
AS OF 1230 PM THURSDAY...THE MEDIUM RANGE MODEL CONSENSUS PROVIDES 
GOOD CONTINUITY FROM INHERITED FCST TO START OFF THE WORKWEEK. STILL 
EXPECTING SFC RIDGING TO BE NOSED SSWD INTO THE CWFA WHILE UPPER 
RIDGE AXIS BUILDS INTO THE EASTERN CONUS. SENSIBLE WX WILL FEATURE 
MAX TEMPERATURES ABOUT 5 DEG F BELOW CLIMO WITH POSSIBLY A FEW 
SHOWERS FORCED BY THE EASTERLY LLVL FLOW. SUPPRESSED ORIENTATION TO 
ATMOSPHERE LOOKS TO CONTINUE INTO TUESDAY WITH EFFECTIVELY MINIMAL
SHOWER CHANCES AND TEMPERATURES PERHAPS WARMING A FEW DEG F.
DEEPER LAYERED RIDGING IS PROGGED TO BREAK DOWN DURING THE LATTER 
HALF OF THE PERIOD...ALLOWING TEMPERATURES TO CLIMB BACK TO NORMAL 
AND PERHAPS THUNDERSTORM CHANCES RETURNING BY THURSDAY.

&&

.AVIATION /19Z THURSDAY THROUGH TUESDAY/...
AT KCLT...THE MIXING OUT OF DEWPOINTS HAS LED TO A FAIRLY PALTRY 
CUMULUS FIELD THIS AFTN. STILL ANTICIPATE THAT MOST OF THE LATE DAY 
CONVECTION WILL PASS NORTH OF THE INTERSTATE 40 CORRIDOR ASSOCIATED 
WITH AN MCS OR CLUSTER MOVING E FROM KY AND WV. WILL ADVERTISE JUST 
A LITTLE INCREASE IN VFR CLOUDS THROUGH THE EVENING 
HOURS...TRANSITIONING TO MID AND HIGH DEBRIS CLOUDS FOR THE 
OVERNIGHT. NW SFC WINDS EARLY ARE EXPECTED TO TOGGLE TO WSW THIS 
EVENING AND THEN RETURN TO NW THROUGH FRIDAY MORNING WITH SLOWLY 
IMPROVING MIXING. ANY CONVECTIVE CHANCES FOR NW NC LOOK RELEGATED TO 
THE AFTN PERIOD FRI AND WILL NOT BE MENTIONED IN THE CURRENT KCLT 
TAF THROUGH 18Z.

ELSEWHERE...ANY ISOLD TO SCATTERED CONVECTION DEVELOPING ALONG THE 
TRAILING END OF AN MCS OR CONVECTIVE CLUSTER PASSING N OF THE REGION 
THIS EVENING SHOULD STAY MAINLY N OF KAVL TO KHKY. GIVEN THE 
POTENTIAL FOR ADDITIONAL RIDGE TOP CONVECTION ADVECTING E IN THE 
WESTERLY STEERING FLOW...WILL RETAIN A VCTS MENTION AT THE NC 
SITES...BUT KEEP THE SC SITES COMPLETELY DRY. EXPECT MAINLY FEW TO 
SCT CUMULUS SOUTH...WITH LITTLE MORE THEN BRIEF VFR CIGS ACROSS THE 
NRN TIER THROUGH EVENING...WITH LINGERING MID AND HIGH DEBRIS CLOUDS 
OVERNIGHT. THE HIGH CLOUDS MAY HELP TO CURTAIL FOG FORMATION...AND 
THE RELATIVELY DRY MIXING OF DEWPOINTS THIS AFTN ALSO SUGGESTS THAT 
ANY IFR FOG WOULD BE CONFINED TO JUST THE SW MTN RIVER VALLEYS NEAR 
DAYBREAK. WILL KEEP ALL TAFS DRY ON FRI THROUGH 18Z. EXPECT MAINLY 
LIGHT W TO NW WINDS...BRIEFLY GUSTY AT KAVL THIS AFTN...TOGGLING SW 
IN SC OVERNIGHT. WINDS WILL COME UP FROM THE NW WITH MIXING 
THROUGHOUT ON FRI MORNING.

OUTLOOK...A SIMILAR PATTERN TO LATE THU IS EXPECTED FRI AFTN AND FRI 
NIGHT...WITH MAINLY FAR NRN TIER SCT CONVECTION POSSIBLE. A BACKDOOR 
COLD FRONT WILL SAG INTO THE REGION THROUGH THE WEEKEND...WITH 
CHANCES OF RESTRICTIONS INCREASING AT KHKY AND KAVL. A MORE DIURNAL 
PATTERN OF EARLY MORNING LOW CLOUDS/FOG AND SCATTERED AFTN TSTMS MAY 
RETURN EARLY NEXT WEEK.

CONFIDENCE TABLE...

            18-24Z        00-06Z        06-12Z        12-18Z 
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%     
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%     
KAVL       HIGH 100%     HIGH 100%     HIGH  85%     HIGH  87%     
KHKY       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%     
KGMU       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%     
KAND       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%     

THE PERCENTAGE REFLECTS THE NUMBER OF GUIDANCE MEMBERS AGREEING
WITH THE SCHEDULED TAF ISSUANCE FLIGHT RULE CATEGORY. COMPLETE
HOURLY EXPERIMENTAL AVIATION FORECAST CONSISTENCY TABLES AND ENSEMBLE
FORECASTS ARE AVAILABLE AT THE FOLLOWING LINK: (MUST BE LOWER CASE)

WWW.WEATHER.GOV/GSP/AVIATION_TABLES

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
NC...NONE.
SC...NONE.

&&

$$
SYNOPSIS...CSH
NEAR TERM...HG
SHORT TERM...JDL
LONG TERM...CSH
AVIATION...HG

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